First implementation of multi-line support.
Remove trailing empty lines before converting to ' \\ '

Not doing so results in the storage engine removing the last
trailing space and thus obstructing the ' \\ ' construct.
Restored original AutoCompleteEdit and moved multi line features to separate class.
Added Menu option to toggle multiline support.
Enable/disable multiline edit control according to preferences.
Introduced feature array and preliminary implemented line ending conversion in lib
HTMLizer to query task instance for newline support.
Reload file when toggling multiline.
Toggle multiline in task editor again.
Save dimensions of task edit window.
Only one cenbtral instance of Settings object
Save dimensions only for multiline edit dialog.
Adapted testcases.
Some more testcases to parse newline.